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E.C. Kim, M. Srinivasan, P. Lalitha, D. Jayashree, V. Cevallos, J.P. Whitcher; Correlation of Corneal Scraping Smear Examination and Presence of Hypopyon to Microbial Culture Results in Suspected Infectious Keratitis . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3584.
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Infectious keratitis can lead to corneal opacification, listed as the 4th most common cause of blindness by the WHO in 2002. Earlier studies from Hyderbad, India concluded that while potassium hydroxide (KOH) + calcofluor white (CFW) are sensitive for fungal keratitis, Gram stain had low sensitivity (39%) in detecting bacteria in bacterial keratitis. Here we reassess the utility of both bacterial and fungal smear evaluation in the initiation of treatment for suspected infectious keratitis.
Microbiological data from suspected infectious keratitis cases presenting to the Aravind Eye Hospital cornea service during a 3 month period was obtained prospectively. At initial exam, smears (Gram, Giemsa, KOH) and comprehensive cultures were obtained.
The results of 434 patients with corneal infectious keratitis were reviewed. Cultures were positive for bacteria, fungus, or acanthamoeba in 299 patients (68.9%), including 48% fungal, 48% bacterial, 3% mixed, and 1% acanthamoeba. Hypopyon was present in 232 patients (53%). The difference in number of patients with hypopyon in fungal (n=81) vs bacterial (n=84) keratitis was not statistically significant (P = 0.825, Χ2 ).
Smear evaluation is of great potential therapeutic relevance due to the rapidity of results provided to the physician. In our hands, Gram stain has relatively high sensitivity, specificity, and predictive values in bacterial keratitis as compared to earlier published studies, and thus plays a role in the its early diagnosis and management. KOH and Giemsa stain for fungal keratitis has a similarly high sensitivity, specificity, and predictive values as previous studies. Both Gram and KOH/Giemsa stains are useful in confirming the diagnosis of bacterial and fungal keratitis, targeting therapy. The presence of hypopyon is not a helpful clinical sign in differentiating between bacterial and fungal keratitis.
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